Front end loader



B. A. Kul-IL FRONT END LOADER Feb. 5, 1963 2 Sheets-Sheet 1 Filed April 22, 1960 BERNARD A. KUHL m'y, .omuf

ATTORNEYS Feb. 5, 1'963 Filed April 22. 1960 B. A. KUHL FRONT END LOADER 2 Sheets-Sheet 2 INVENTOR.

BERNARD A. KUHL ATTORNEYS United States Patent() 3,076,571 FRONT END LOADER Bernard A. Kohl, Lakewood, Ohio, assignor to The Thew Shovel Company, Lorain, Ohio, a corporation of Ohio Filed Apr. 22, 1960, Ser. No. 24,062

7 Claims. (Cl. 214-440) VThe present invention relates generally as indicated to a front end loader and more particularly -to a front end loader of the type that comprises a pair of longitudinal side booms pivoted at their rear ends to the tractor and at their front ends to the lower rear portion of a material handling scoop; a hoist cylinder for swinging said booms and scoop in a vertical plane about the boom-tractor pivot; and a scoop actuating cylinder and linkage arrangement effective to tip the scoop for scooping up a `load and for dumping 4the load.

It is known, of course, to provide front end loaders having side booms that are of angular form to provide, in digging position, upper rear portions pivotably connected with the tractor and extending generally downward from such pivot; intermediate portions extending generally forwardly between the tractor body and the re` spective front wheels thereof; lower front portions extending downwardly and forwardly for pivotal connection with the bottom rear portion of the scoop. It is known to provide in equipment of this type, a scoop actuator which comprises, for example, hydraulic cylinders which have one end linked to the respective booms and the other end pivotally connected to the scoop at the rear thereof at points above the boom-scoop connections. Accordingly, by -actuating said cylinders, the scoop may be tipped back from digging position to retain a load of material therein, and as the booms are swung upwardly, the linkage aforesaid -including the booms, being a departure from true parallelogram linka-ges, elect a gradual tipping back of the scoop to horizontal maximum load supporting position .at a rate less than the angular movement of the .booms from digging position to maximum lift position. With the booms thus raised, theaforesaid `cylinders are actuated to tip the scoop forwardly and thereby dump the contents thereof.

It is one object of the present invention to provide a front end loader linkage of the character indicated in which the links thereofV are disposed within the lateral limits of the respective side booms so as to be protected against dirt and damage.

It is another .object of this invention to provide a front end loader of the character indicated which employs curved link-s which are arranged to have higher deilection rates under load than corresponding straightrlinks heretofore employed in prior art loaders of this character, such curved links, more specifically herein generally S- shaped links, by reason of their higher deilection rates being capable of absorbing shocks and impact loads due to digging .action etc. whereby pivot pin wear and break- -age is substantially decreased.v

Itis another object of this invention to provide a front end loader -of the character indicated in which the curved links aforesaid are arranged to contribute to the compactness and simplicity of the boom assembly, especially in the regions at the opposite sides of the operator.

It is another object of this invention to provide a front end loader `of the character indicated in which the geometry of the scoop and boom linkages is such as to obtain better ranges insofar as hoisting heights and reaches are concerned in relation to the length of the booms and their angles of swing between digging and hoist positions.

It is another object of this invention to provide a front end loader in which the side booms have safety arms or links which, though pivotally connected to the tractor a substantial distance `behind Vthe back rest ofthe operators ICC seat and steering wheel, preclude injury to the operator and provide for clear side and rear visibility by the operator of the equipment even in the fully raised position of the booms.

It is another 4object of this invention to provide hoist cylinders which, in the digging position of the booms, are disposed in a generally horizontal position and which swing upwardly as the booms are swung upwardly while yet providing a substantial moment arm to enable use of fluid at relatively lower pressure than in known prior art structures. t

It is another object of this invention to provide a front end loader in which the hoist cylinders are disposed entirely clear of the steering wheels of the tractor to allow a greater wheel cut and consequently a shorter .turning radius of the tractor. V

`It is yet another object of this invention to provide hoist cylinders as aforesaid, which are so disposed within the respective booms that in the event of leakage or bursting of the rod packings, the operator is fully protected against` injury by hot oil squirting from such defective packings.

Yet another object of this invention is to provide a compact front end loader in which all of the component members of the boom-scoop assembly are subjected to digging loads, whereby such loads are distributed among4 the said members to thus avoid any unduly bulky components.

Still another object of this invention is to provide a front end loader which,'in the maximum hoist position,

has cooperating stops on the boom and the scoop eifective,

when the scoop is tilted to dumping position, to shake or jar the scoop so as to free the contents ythereof for sliding out,

Still another object of this invention is to provide a front end loader in which the scoop actuator provides the dumping stops in the maximum reach position of theboom but a resilient connection is provided between the actuator and the scoop so that the impact of dumping loads .on the actuator is substantially lessened.

Still another object of this invention is to provide a ceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the featureshereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail a certain illustrative embodi-V ment of the invention, this being indicative, however, ofl

but one of the various ways in which the principle of the invention may be employed.

In said annexed drawings: Y

FIG. 1 is a side elevation view of a front end loader according to the present invention, the boom and Scoop being shown in its lowered digging position in full lines in which position the scoop is held while the loader is driven into a pile of gravel, sand or other material which it is desired to scoop up and load into a truck or to dump elsewhere, FIG. l also showing in dot-dash lines the initial tilt-back position, wherein the material is scooped into the scoop as the loader continues to move into the pile of material, and also showing in dot-dash lines a portion of the scoop in the position it assumes as the boom is raised;

FIGS. 4 and S are side elevation views similar to FIG. l respectively showing the positions of the loader components when the boom is raised to maximum height and when the boom is lowered from maximumA height to provide for added reach.

` Referring now more specifically to the drawings, and

irst `to FIG. l, the front end loader herein comprises a tractor 1, having front and rear wheels 2 and 3 all of which are engine-driven and of which the rear wheels 3 are, the steering wheels actuated by the steering wheel 4 provided near the front end of the tractor 1. Behind the steering wheel 4 is the operators seat 5 which includes the usual back rest 6. At the front end of the tractor 1 is a block of rubber 7 or the like, that constitutesa bumper so that lthe tractor may be driven against the side of a truck body when the boom 8 is in the raised position containing a load of material in the scoop 9 thereof which it is desired to dump into the truck body.

'Ihe loader herein comprises a pair vof parallel angular booms 8. which have their rear and upper ends pivotally connected by pins 10 to the brackets 11 aixed on opposite sides of the tractor 1 at a zone which is spaced a substantial distance to the rear of the back rest 6 of the operators seat and a substantial distance below the top edge of the back rest 6. The lower front ends of the booms 8 are pivotally connected by pins 12 to the lower rear portion and adjacent the ends of the scoop 9.

y As best shown in FIGS. 2 and 3, each boom 8 cornprises a pair of parallel side plates 14 joined together by a topweb plate 15 whichin the digging position of the boom '8, extends downwardly and forwardly from adjacent the boom pivot and by another top web plate 16 of generally V-shaped transverse cross-section which extends downwardly and forwardly along the downwardly and forwardly extending front portion of the boom 8 at a zone. spaced rearwardly from the boom-scoop pivot 12. There is also a rear web 17 disposed across the rear edges of the side plates 14. The front end portions of the booms 8 are joined together as by a transversely extending tubular brace member 18 having its ends securely attached, as -by welding, or equivalent expedient, to the respective booms 8.

Pivotally connected to each boom 8 by pin 19 between the top webs l and 16 is an S-shaped link 20, one end of which, in turn, is pivotally connected by the pin 21 to the cylinder 23 of the double acting scoop-actuating piston-cylinder assembly 24. The piston rod 2S of the scoop-actuator 24 is pivotally connected by the pin 26 to the scoop 9 at a zone which is substantially directly above the connection of the boom 8 with the scoop 9 when boom and scoop are in FIG. 2 digging position. `In this condition of the parts, the scoop-actuator 24 is partly extended so that when the piston `rod 25 is fully retracted in the cylinder 2.3,V the scoop 9 will be tilted back about 37 up from horizontal as shown in dotdash lines in FIG. 1. As the scoop 9 is lthus tilted back, the cylinder 23 swings down about pin 21 but clears the web 16- by reason of the special shape of the latter. Normally, the operator drives the tractor 1 into the bottom of the pile while the boom 8 is down and the scoop 9 is in digging position, as shown in full lines in FIG. l, and after the scoop 9 has penetrated the pile, the operator actuates an appropriate valve (not shown) to fully retract the scoop actuator 24 to the aforesaid 37 position while the tractor 1 continues to move into the pile., At the same time, the operator actuates another valve (not shown) to swing the boom 8 up about the boom pivot 10. As the boom 8 swings up, the scoop 9 tilts back but not in direct relation to the angle of swing of the boom 8 by reason of the provision of a linkage mechanism hereinafter described.

In order Vthat the scoop4 9 be tilted back at a slower rate than the rate of angular movement of the boom 8 to thus enable raising of the boom to a greater maximum height, the lower end of the S-shaped intermediate link 20 is pivotally connected by the pin 27 to the lower front end of another S-shaped link 28 which has its upper rear end pivotally connected by a pin 29 to a bracket 30 which is xed on the tractor 1 preferably at a point below and forward of the boom pivot pin 10.-

This longer link 29 is of the same general shape as' the boom 8 so as to be substantially entirely within the' side plates 14 in all positions of the boom 8.

It is to be noted that the pairs off pins 10 and 29 and 19 and 27, and -the pairs of pins 21 and 19 and 26 and 12, do not constitute the corners of parallelograms, and that by reason of their particular disposition as herein shown, the swinging of the boom 8 from digging position (FIG. l) tothe maximum hoist position (FIG. 4) through an angle of say about 74, the scoop 9 only swings about 24, from its 37 position in the tilted back digging posiytion to the 61 maximum height and capacity position. In other words, as clearly shown in FIG. 4, the intermeditae S-shaped link 20 has been swung clockwise durin'g the upwardr swinging movement of the boom 8 through `the long S-shaped link 28 due to swinging of the front en'd of link 28 about the axis of the pin 29 while the boomshort link pivot 119 swings about the axis of the boom pivot 10. In the maximum height position, the scoop 9 is in maxim-um load-carrying position and when it is desired to dump the contents of the scoop the operator actuates a valve (not shown) to open the rod end of the scoop-actuating cylinder 23 to `a Vent through large size tubing, and, atl Ithe same time, to introduce fluid under pressure from an engine-driven pump (not shown') into the head end of the cylinder 23, whereby the scoop 9 will be swung clockwise about its pivot connection 12 to the tip of the boom 8. As the scoop 9 swings to dumping position, a stop 31 on the scoop 9 engages a stop 32 on the boom 8, whereby to jar the contents of the scoop 9 for ready sliding therefrom. In this dumping position, the angle A from horizontal is preferably about 51.

In this FIG. 4 dot-dash line dumping position of the scoop 9, the lip 34 of the scoop is 3'0" from the front peripheries of the wheels 2 (dimension B) and nearly l0 from the ground (dimension C). When it is necessary to reach further as into a wide body truck or railroad car, the boom 8 may be lowered about 12 to the FIG. 5 position in which .the dumping position angle D is about 46 and the lip 34 thereof is spaced about 451/2 (dimension E) from the `front peripheries of the wheels 2 while the lip 34 is 86" (dimension F) from the ground.

At the maximum hoist position' of .the boom 8 and with the scoop 9 in dumping position with the stops 31 and 32 engaged with one another, the piston 25 in the cylinder 23 is not quite at the end of its stroke, whereby no shock loads are imposed on the cylinder end cap 35 by the piston 25.

However, in other positions of the boom 8, the stops 31 and 32 do not quite engage. Therefore, in order to absorb inertia shock loads of the scoop 9 that otherwise would be transferred from the piston 2S to the end cap 35 of the cylinder 23, there is provided a rubber bushingl 36, at least around the pin connection 26 of the piston rod 25 to the scoop 9.

As aforesaid, the indentation in the Aweb 16 of the boom 8 accommodates the cylinder 23 as when the scoop 9 is tilted back from the digging position. The slot 37 in the lower front end of the web 116 accommodates .the scoop supports 38.

The hoist cylinder 40 is preferably disposed in generally horizontal position and substantially entirely within the contines ofthe side plates 14 of the boom 8 when the latter is in digging position. Thus, the piston rod 41 of the hoist cylinder 40 is connected by the pin 42 to a bracket 43 on the tractor 1 at a point spaced a substantial distance below the boom pivot 1,0 and the long S-arm pivot 29. As shown, the top and bottom portions 45 and i 46 of the long S-arm 28 are cut away to accommodate the hoist cylinder 40 which extends between the opposite sides of said long S-arm 28. The cylinder 40 near its rod end has a trunnion 47 `affixed thereto which is journalled in the opposite side plates 14 of the boom 8 at a region which is below and forward with respect to the boom and long arm pivots and 29, the side plates being reinforced as by bosses 48 Welded thereto. Accordingly, when the boom 8 is raised, the operator -actuates a valve (not shown) to allow fluid under pressure to enter the head end of the cylinder 40, whereby the cylinder is moved with respect to the piston 41 to swing the boom 8 about its pivot 10. Even in the maximum height position of the boom 8 (FIG. 4) the hoist cylinder 40 acts through a substantial moment arm G about 2/3 of the maximum) so as not to require the use of extremely high pressure fluid or an unduly large cylinder. It is further to be noted that in the maximum hoist position of lthe boom 8 'the rod packing 49 is disposed within the side plates 14 yand beneath web 15 to thus protect the operator from injury in the event of leakage or lbursting of such rod packing.

Another feature of the present invention is `that by reason of the disposition of the boom pivot I1li a substan- `tial distance to the rear of and below the top edge of the back rest 6, the boom 8 in its maximum hoist position may extend forwardly and upwardly as shown in FIG. 4 without impairing the operators lateral visibility while seated on the seat 5.

From the foregoing, it can be seen that the present invention is of simple and compact form and enables lifting of the scoop to relatively great heights while providing adequate reach in relation to ,the length of boom 8. Also, a relatively small hoist cylinder 40 may be employed in nesting relation with the boom 8 and S-shaped link 28. Furthermore, the links and 28 are shaped to clear each other and the boom 8 aside from the higher deflection ra-tes thereof under load than corresponding straight links. In' the digging position, and with uid under pressure in the hoist and scoop actuating cylinders 40 and 23, the digging loads are distributed among all of the components of the front end loader herein whereby none of the components need be orf heavy and bulky form. Even the hooms 8 are of S-shaped form having higher deflection rates than comparable straight booms extending downwardly and forwardly from the boo-rn pivots l0. This yielding of .the components herein prevents application of heavy shock or impact loads on the pins thereof with consequent greater pin life.

Although in the present case a portion of the loader arm geometry is disposed to the rear of the operator, it is to be understood that the loader herein may be mounted on any desired portion of the tractor 1 with, :for example, mhe boom pivot 10 disposed forwardly with respect to the operators seat 5.

IOther modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

l. A front end loader comprising a mobile tractor having ground-engaging propelling means and a forwardly facing operators seat from which the operator may control the movements of said tractor; and a forwardly extending material handling assembly and actuating means therefor pivotally mounted on said tractor for swinging in a vertical plane from a lower material pickup position to an upper hoist and dump position; said assembly comprising a pair of hollow booms having rear portions ywhich are pivotally connected to the respective sides of said tractor rearward of said Seat and which, when said booms are in such lower position, extend downwardly and forwardly from such boom pivot, said booms also having front portions disposed forwardly of the front end of said tractor and close to the ground when said booms are in such lower position; a material handling scoop pivotally connected to the front ends of said booms for tilting movements about a horizontal axis for scooping material therein and for dumping such material therefrom; and a three-part linkage associated with each boom for tilting said scoop to different angular positions with respect thereto, said linkage comprising a first link disposed substantially in its entirety within said boom and pivotally connected at one end to said tractor vat a point below the boom-tractor pivot, an intermediate link pivotally connected between its ends to an intermediate portion of said boom, and a third variable length link pivotally connected at its respective ends to said scoop in radially spaced relation to the boom-scoop pivot effective to tilt said scoop to different angular positions relative to said boom in response to change in length of said third link and to one end of said intermediate link, the other ends of said first and intermediate links being pivotally connected together, the pivot connections of said boom and said first link to said tractor and of said intermediate link to said boom and to said first link defining the corners of an articulated quadrangle which changes the angular position of said scoop with respect to said boom as the latter is swung about the boom pivot, said first link being of generally S-shaped form curving -downwardly and forwardlyfrom such one end `and thence downwardly and forwardly toward such other end when said boom is in such lower position, and wherein said intermediate link is of generally S-shaped form curving upwardly and forwardly from such other end to its pivot connection with said boom and thence extending upwardly curving successively rearwardly and forwardly tow-ard such one end.

2. The front en d loader of claim l wherein a hoist cylinder is provided in operative association with each boom to swing said assembly as aforesaid, said cylinder having one end pivotally connected to said tractor at a point below the boom and first link pivotal connections with said tractor and extending generally horizontally into said boom when the latter is in such lower position, and having an intermediate portion pivotally connected to said boom to swing the latter upwardly when said cylinder is extended. v

3. The front end loader of claim l wherein a hoist cylinder is provided in operative association with each boom to swing said assembly as aforesaid, said cylinder having one end pivotally connected to said tractor at a point below the boom and first link pivotal connections with said tractor and extending generally horizontally into said boom when the latter is in such lower position, and having an intermediate portion pivotally connected to said boom to swing the latter upwardly when said cylinder is extended, said first link being formed with an opening between its ends through which the other end of said cylinder extends.

4. A boom and scoop assembly comprising a pair of hollow generally S-shaped booms which, in their lower material pickup position, extend downwardly and forwardly from their upper ends and thence downwardly and forwardly toward their lower ends, a support to which the upper ends of said booms are pivotally connected for swinging in vertical planes from such lower position to an upper hoist and dump position, a scoop pivotally connected to the front ends of said booms for tilting movements to different angular positions with respect to said boom to scoop material therein, to hoist such material responsive to upward swinging of the front ends of said booms, and to dump such material therefrom, and a pair of link assemblies extending from pivot points on said support through the respective booms to pivot points on said scoop radially spaced from the respective boomscoop pivots, said link assemblies including first links of generally S-shaped form extending substantially longitudinally within said booms curving downwardly and for- `wardly from pivotal connections at their upper ends with said support and thence curving downward-1y and forwardly toward their lower ends, second links having lower ends pivotally connected to the lower ends of the respective first links and having intermediate portions pivotally connected intermediate the ends of the respective booms, and third variable length links having their ends pivotally connected to the upper ends of therespective second links and to said scoop as aforesaid operative when increased in length to tilt said scoop to material dump position, the pivotal connections of said booms and first links with said support, of said second links with said booms, and

of said first and second links with each other deining the corners of articulated quadrangles effective to tilt said scoop with respect to said booms as the latter are swung upwardly from such lower position to an upper hoist position from which the material therein may be dumped by extending said third links, said second links being also of generally S-shaped form curving upwardly and forwardly from their lower ends and thence extending upwardly and curving rearwardly and forwardly toward their upper ends when said booms are in such lower position.

5. The assembly of claim 4 wherein extensible hoist means are operatively associated with the respective booms to swing them from lower to upper position, said hoist means extending generally horizontally within the respective booms in the lower position of the latter and having rear ends pivotally connected to said support at points below the respective boom and first link pivot connections with said support and having intermediate portions pivotally connected to the respective booms.

6. The assembly of claim 4 wherein extensible hoist means are operatively associated with the respective booms to swing them from lower to upper position, said hoist means extending generally horizontally within the respective booms in the lower position of the latter and having rear ends pivotally connected to said support at points below the respective boom and first link pivot connections with said support and having intermediate portions pivotally connected to the respective booms, and wherein said first links have openings between their ends through which the front ends of the respective hoist means extend when said booms are in such lower position.

7. A front end loader comprising a mobile tractor having ground-engaging propelling means and a forwardly facing operators seat from which the operator may control the movements of said tractor; and a forwardly extending material handling assembly and actuating means therefor pivotally mounted on said tractor for swinging in a vertical plane from a lower material pickup position to an upper hoist and dump position; said assembly comprising a pair of hollow booms having rear portions which are pivotally connected to the respective sides of said tractor rearward of said seat and which, when said booms are in such lower position, extend downwardly and forwardly from such boom pivot, said booms also having front portions disposed forwardly of the front end of said tractor and close to the ground when said booms are in such lower position; a material handling scoop pivotally connected to the front ends of said booms for tilting movements about a horizontal axis for scooping material therein and for dumping such material therefrom; and a three-part linkage associated with each boom for tilting said scoop to different angular positions with respect thereto, said linkage comprising a rst link disposed substantially in its entirety within said boom and pivotally connected at one end to said tractor at a point below the boom-tractor pivot, an intermediate link pivotally connected between its ends to an intermediate portion of said boom, and a third variable length link pivotally connected at its respective end-s to said scoop in radially spaced relation to the boom-scoop pivot effective to tilt said scoop to different angular positions relative to said boom in response to change in length of said third link and to one end of said intermediate link, the other ends of said rst and intermediate links being pivotally connected together, the pivot connections of said boom and said first link to said tractor and of said intermediate link to said boom and to said tirst link defining the corners of an articulated quadrangle which changes the angular position of said scoop with respect to said boom as the latter is swung about the boom pivot, said booms and scoop being provided with interengageable stops to jar said scoop when said third link is extended in an upper position of said assembly, and wherein the third link-scoop pivot includes a yieldable component effective to reduce inertia loads on said third link when fully extended in an intermediate position of said assembly and prior to interengagement of said stops.

References Cited in the tile of this patent UNITED STATES PATENTS Re. 24,746 Pilch Dec. 8, 1959 337,761 French Mar. 9, 1886 2,846,097 Beyerstedt Aug. 5, 1958 2,876,921 Salma Mar. 10, 1959 

1. A FRONT END LOADER COMPRISING A MOBILE TRACTOR HAVING GROUND-ENGAGING PROPELLING MEANS AND A FORWARDLY FACING OPERATOR''S SEAT FROM WHICH THE OPERATOR MAY CONTROL THE MOVEMENTS OF SAID TRACTOR; AND A FORWARDLY EXTENDING MATERIAL HANDLING ASSEMBLY AND ACTUATING MEANS THEREFOR PIVOTALLY MOUNTED ON SAID TRACTOR FOR SWINGING IN A VERTICAL PLANE FROM A LOWER MATERIAL PICKUP POSITION TO AN UPPER HOIST AND DUMP POSITION; SAID ASSEMBLY COMPRISING A PAIR OF HOLLOW BOOMS HAVING REAR PORTIONS WHICH ARE PIVOTALLY CONNECTED TO THE RESPECTIVE SIDES OF SAID TRACTOR REARWARD OF SAID SEAT AND WHICH, WHEN SAID BOOMS ARE IN SUCH LOWER POSITION, EXTEND DOWNWARDLY AND FORWARDLY FROM SUCH BOOM PIVOT, SAID BOOMS ALSO HAVING FRONT PORTIONS DISPOSED FORWARDLY OF THE FRONT END OF SAID TRACTOR AND CLOSE TO THE GROUND WHEN SAID BOOMS ARE IN SUCH LOWER POSITION; A MATERIAL HANDLING SCOOP PIVOTALLY CONNECTED TO THE FRONT ENDS OF SAID BOOMS FOR TILTING MOVEMENTS ABOUT A HORIZONTAL AXIS FOR SCOOPING MATERIAL THEREIN AND FOR DUMPING SUCH MATERIAL THEREFROM; AND A THREE-PART LINKAGE ASSOCIATED WITH EACH BOOM FOR TILTING SAID SCOOP TO DIFFERENT ANGULAR POSITIONS WITH RESPECT THERETO, SAID LINKAGE COMPRISING A FIRST LINK DISPOSED SUBSTANTIALLY IN ITS ENTIRETY WITHIN SAID BOOM AND PIVOTALLY CONNECTED AT ONE END TO SAID TRACTOR AT A POINT BELOW THE BOOM-TRACTOR PIVOT, AN INTERMEDIATE LINK PIVOTALLY CONNECTED BETWEEN ITS ENDS TO AN INTERMEDIATE PORTION OF SAID BOOM, AND A THIRD VARIABLE LENGTH LINK PIVOTALLY CONNECTED AT ITS RESPECTIVE ENDS TO SAID SCOOP IN RADIALLY SPACED RELATION TO THE BOOM-SCOOP PIVOT EFFECTIVE TO TILT SAID SCOOP TO DIFFERENT ANGULAR POSITIONS RELATIVE TO SAID BOOM IN RESPONSE TO CHANGE IN LENGTH OF SAID THIRD LINK AND TO ONE END OF SAID INTERMEDIATE LINK, THE OTHER ENDS OF SAID FIRST AND INTERMEDIATE LINKS BEING PIVOTALLY CONNECTED TOGETHER, THE PIVOT CONNECTIONS OF SAID BOOM AND SAID FIRST LINK TO SAID TRACTOR AND OF SAID INTERMEDIATE LINK TO SAID BOOM AND TO SAID FIRST LINK DEFINING THE CORNERS OF AN ARTICULATED QUADRANGLE WHICH CHANGES THE ANGULAR POSITION OF SAID SCOOP WITH RESPECT TO SAID BOOM AS THE LATTER IS SWUNG ABOUT THE BOOM PIVOT, SAID FIRST LINK BEING OF GENERALLY S-SHAPED FORM CURVING DOWNWARDLY AND FORWARDLY FROM SUCH ONE END AND THENCE DOWNWARDLY AND FORWARDLY TOWARD SUCH OTHER END WHEN SAID BOOM IS IN SUCH LOWER POSITION, AND WHEREIN SAID INTERMEDIATE LINK IS OF GENERALLY S-SHAPED FORM CURVING UPWARDLY AND FORWARDLY FROM SUCH OTHER END TO ITS PIVOT CONNECTION WITH SAID BOOM AND THENCE EXTENDING UPWARDLY CURVING SUCCESSIVELY REARWARDLY AND FORWARDLY TOWARD SUCH ONE END. 